1. Field of the Invention
The present invention generally relates to an improved oil well production tube system. More specifically, the present invention relates to an oil well production tube system where one or more smaller coilable power tubes is placed within a larger coilable production tube.
2. Background Information
The use of coilable production tubing for the transfer of fluid from a subterranean source to the surface is known in the art. However, such production tubing systems heretofore devised and utilized are known to consist basically of familiar, expected and obvious structural configurations, notwithstanding the several designs encompassed by the prior art which have been developed for the fulfillment of many objectives and requirements. While these devices may fulfill their respective, particularly claimed objectives and requirements, the aforementioned devices do not disclose an improved oil well production tube system such as Applicant's present invention.
Conventional artificial lift recovery systems employ a series of rigid, individual production tube segments joined to one another by threading each segment together. Typically, these segments are on the order of thirty feet in length. Each individual link is connected to the next so as to form a final production tube extending between the surface and bottom of a well. Several problems are unavoidable with systems employing this type of production tubing. For example, a rigid, segmented production tube is prone to leaking recovered fluid about the point where individual segments are joined together. These problems are exaggerated when a well bore becomes warped or deviated; as such, many times rigid segments cannot be used in multiple well bores. Further, individual production tube segments are subject to cross-threading or other thread damage that may compromise the mechanical integrity of the production tube. When this occurs, heavy machinery (capable of producing high torque) must be used to unthread or separate individual segments from one another. Finally, in the event the production tubing must be removed from the well bore, individual segments must be taken out of the ground in linear fashion, extending several feet above the surface, before they can be completely removed from the well.
Commonly, artificial lift recovery systems employ electrical cables to power a downhole pump. However, these types of systems present several problems. For instance, electrical cable must be strapped to the outside of each individual joint with bands or straps to hold the cable in place. This involves the use of at least two additional personnel and a spooling unit. One person is needed to run the banding machine that attaches the cable to the production tube and another person is needed to run the electrical cable spooling unit that contains the spool of electrical cable. Moreover, the cable itself must be sheathed in a protective shield, or armor, to protect against abrasions that might occur during installation. Even when this protection is utilized, cable damage can occur that causes an electrical short in the cable when power is applied. The production tube and cable must then be pulled from the well bore and repaired before it can be run back into the well bore.
It is not uncommon for the bands that hold electrical cable to break or be installed improperly. When this occurs, since the armored electrical cable is not capable of supporting its own weight for the entire length of the production assembly, other straps break, ultimately resulting in a cable failure. In such an event, cable recovery from the well bore is an expensive and often unsuccessful process. Additionally, occasionally the production tube disjoins and subsequently severs the electrical cable; of course, such a combination is especially difficult to retrieve from the well bore.
Other practical difficulties are associated with the use of electrical cables in artificial lift recovery systems. Specifically, as a result of gaps between the electrical cable and production tube, and the electrical cable and protective armor, current blowout preventers can not achieve a 100% positive seal. Moreover, in wells that have the potential for heavy flowing, brine water must be constantly pumped in the well bore while the pump is being installed. Also, the well bore inside diameter must be large enough to house both the production tube and the electrical cable, which of course, limits the installing of large capacity pumps in smaller diameter well bores.
In view of the preceding, Applicant submits that hydraulically powered downhole pumping systems are much more effective. Nevertheless, seemingly unavoidable problems are a major concern for those skilled in the art. Use of a single coilable production tube provides no means for efficient hydraulic power communication between the surface and a downhole recovery device. Specifically, the use of coliable production tube, alone, does not provide for efficient or reliable power communication between the surface and a downhole recovery device. Limitations of known coilable tube production systems are also grounded in their manufacturing process. Known coilable production tube manufacturing processes do not lend themselves to placing smaller coilable, power tubes within a larger coilable production tube. Specifically, no fabrication process has been developed to allow for such a configuration. In the alternative, continuous power tube may be “guided” along the production tube from surface to downhole. However, this procedure is far from practical as binding, kinking, and sliding friction make for an all to difficult task.